1. Field of the Invention
The present invention generally relates to a wheel support bearing assembly for an automotive vehicle or the like and, more particularly, to the wheel support bearing assembly integrated with a magnetic encoder for detection of the number of revolution of a wheel.
2. Description of the Prior Art
As shown in FIG. 23, the wheel support bearing assembly is well known, which includes generally cylindrical inner and outer members 101 and 102 positioned one radially inside the other with an annular space defined therebetween, dual rows of rolling elements 103 interposed between the inner and outer members 101 and 102 and rollingly movably positioned within the annular space, an annular sealing device 105 accommodated within and positioned at one of opposite ends of the annular space, and an annular magnetic encoder 106 integrated together with the sealing device 105. This known wheel support bearing assembly is disclosed in, for example, the Japanese Laid-open Patent Publication No. 6-281018.
In this known wheel support bearing assembly, the sealing device 105 includes generally L-sectioned first and second annular sealing plates 107 and 108 press-fitted onto an outer periphery of the inner member 101 and into a bore of the outer member 102, respectively, and an annular sealing strip 109 secured to the second annular sealing plate 108. The first sealing plate 107 is generally referred to as a slinger. The annular magnetic encoder 106 employed therein is in the form of an elastic member (also referred to as a multi-pole magnet) 111 made of a vulcanizable elastic material mixed with a powdered magnetic material and is bonded by vulcanization to the first sealing plate 107. The multi-pole magnet 111 has a plurality of magnetic N- and S-poles alternately defined therein in a direction circumferentially thereof and is operatively associated with a magnetic sensor 110 disposed in face-to-face relation with the multi-pole magnet 111 to detect the number of revolutions of the wheel rotatably supported by the wheel support bearing assembly.
With the known wheel support bearing assembly of the structure discussed above, it has been found that in the event of ingress of foreign matter such as, for example, stones or rocks into a working gap delimited between the multi-pole magnet 111 and the magnetic sensor 110, the multi-pole magnet 111 and, hence, the magnetic encoder 106 may be impaired, resulting in failure to detect the number of revolutions of the wheel properly.